Historically, communications across applications on a given computer network system have had to use fairly complicated Remote Procedure Call (RPC) systems, which generally limit the usefulness of such systems to those languages, runtimes, and/or libraries configured to utilize RPC libraries or frameworks. In the Windows and UNIX systems, a number of APIs have been developed over the years to enable such communications. One problem has been that these systems have typically been fairly complex and access to those APIs (e.g., COM, CORBA, D-Bus, Gconf) requires manual binding into the libraries or frameworks in the system. These systems suffer from various other drawbacks, some of which are described below.
CORBA uses the Internet Inter-Orb Protocol (IIOP) and usually requires a CORBA stack to be available before it is possible to communicate to various components. Availability of CORBA is spotty at best and the size of the specification is large enough that at least some people tend not to use it, and instead implement their own systems. D-Bus is a system bus for broadcasting messages where service providers can post messages that get distributed to one or more applications listening on a given event. D-Bus requires use of its own home-grown protocol to notify multiple clients on the system. COM is the language of the Windows platform used to communicate to components. It is based on a binary interface and suffers for the drawbacks associated with RPC. Gconf is a system for fetching configuration values from a daemon and be notifying the system of changes in the configuration at runtime. Like D-Bus, Gconf uses an internal protocol (it happens to be implemented on top of CORBA).
All these system suffers from various individual drawbacks but one universal disadvantage to these systems is that they are, among other things, proprietary, heavy weight protocols, and difficult to manage across different languages, frameworks and operating systems. One challenge lies in turning desktop applications into web-aware applications. This requires a mechanism that can locate the applications or services that can be implemented with minimal effort and that can be used across different languages, frameworks and operating systems in order for it to gain traction in the real-world usage.
Existing systems suffer from these and other problems.